Moving weightless objects
Moving weightless objects
复制标题
移动失重物体
DOI：
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发表时间：
2000
影响因子：
2
通讯作者：
Norbert Mai
中科院分区：
文献类型：
--
作者：
J. Hermsdörfer;C. Marquardt;J. Philipp;A. Zierdt;Dennis A. Nowak;Stefan Glasauer;Norbert Mai
抽象。当我们移动抓取的物体时，我们的抓握力精确地预测了重力和惯性载荷。我们分析了在抛物线飞行引起的非常大的载荷变化期间的抓地力控制。在这些飞行机动期间，重力在与正常地球重力加倍有关的超重力和20秒的微重力之间变化。因此，物体重量对载荷的贡献从正常值的两倍变为不存在。两名受试者连续进行垂直和水平运动的对象配备了握力和加速度传感器。在正常重力和超重力条件下进行垂直运动时，载荷力最大值出现在下转折点，最小值出现在上转折点，而在微重力条件下，载荷力模式完全改变。特别是，上转折点也与载荷力最大值相关。由两名受试者产生的握力的分析表明，握力经历了相同的特征变化的负载力。因此，受试者能够在不同的和新的负载条件下，在预期的手臂运动引起的负载力的波动，调整握力。在比较垂直和水平运动时，对变化的重力水平的适应也很明显：在正常重力和超重力状态下，抓握力在很大程度上取决于运动方向，但在微重力状态下则不然。即使在重力水平之间的过渡期间，也观察到握力和负载力的预测性耦合，表明快速适应变化的负载条件。为了解释握力控制的正常特征的惊人保存，我们认为，一个高度自动化的，非常灵活的感觉运动机制，坚定地在中枢神经系统内实施，可以科普即使是巨大的环境条件的变化。
Abstract. When we move grasped objects, our grip force precisely anticipates gravitational and inertial loads. We analysed the control of grip forces during very substantial load changes induced by parabolic flights. During these flight manoeuvres, the gravity varies between hypergravity associated with a doubling of normal terrestrial gravity and a 20-s period of microgravity. Accordingly, the contribution of the object's weight to the load changed from being twice the normal value to being absent. Two subjects continuously performed vertical and horizontal movements of an object equipped with grip force and acceleration sensors. Whereas, during vertical movements performed under normal and hypergravity, a load force maximum occurred at the lower turning point and a minimum at the upper turning point, the load force pattern was completely changed under microgravity. In particular, the upper turning point was also associated with a load force maximum. Analysis of the grip forces produced by the two subjects revealed that the grip forces underwent the same characteristic changes as the load forces. Thus, subjects were able to adjust grip forces in anticipation of arm movement-induced fluctuations in load force under different and novel load conditions. Adaptation to changing levels of gravity was also obvious when the vertical and horizontal movements were compared: grip forces depended heavily on movement direction during normal and hypergravity but not during microgravity. The predictive coupling of grip force and load force was observed even during transitions between gravity levels, indicating rapid adaptation to changing load conditions. To account for the striking preservation of the normal characteristics of grip force control, we suggest that a highly automatized, extremely flexible sensorimotor mechanism firmly implemented within the central nervous system can cope with even massive changes in the environmental conditions.